1. Field of the Invention
The present invention relates to a color cinematography camera with solid state imaging sensors. In particular, the invention relates to a scanning wheel-type color camera using plural sensors.
2. Description of Related Art
Color cameras are known. One type of color camera uses a single CCD imaging sensor with a Bayer pattern overlaying color filter. A Bayer pattern overlaying filter uses four sensor elements per pixel. The overlaying color filter, transmits green light into the first and second sensor elements, transmits blue into the third sensor element and transmits red light into the fourth sensor element. The four elements make up one pixel of a digital color camera. This tends to limit the resolution achievable by such color cameras.
Another type of color camera uses expensive prisms and custom lenses and three CCD imaging sensors. Ordinary spherical objective lenses pass the image light into a prism as converging (not parallel) rays of light. Because of dispersion characteristics that any optical material imparts on light passing through the material, the converging (not parallel) rays of light undergo different dispersions since the different rays of light have different path lengths. This leads to noticeable color distortions. To over come this, known cameras use a more complex color corrected objective lens.
In FIG. 29A, known camera 2000 includes lens 2010 to focus an image conjugate through color filter wheel 2050 onto imaging sensor 2040. Color filter wheel 2050 is divided into three color sectors, each sector representing one-third of a circle. Each sector 2052, 2054 and 2056 passes light (i.e., transmits, not reflects) of a different one of the three primary colors (i.e., blue, red and green) (FIG. 29B). A color wheel assembly includes motor 2020 to spin color filter wheel 2050. To obtain a full color image requires that sensor 2040 form three complete images for each revolution of color filter wheel 2050. When the camera system requires that moving images be captured at a particular rate, the time available for capture of each color image is just one-third of the frame time. This limits the sensitivity of the camera.
It should be noted that rotatable color wheels have been used in the projection TV industry (not cameras). For example, see U.S. Pat. Nos. 5,868,482 and 6,024,453.
Interline transfer (ILT) CCD sensors include an electronic shutter function to prevent smear effects. Known cameras require the ILT design to control smear.
It is desired to control smear and provide near synchronous imaging with a 2-chip frame transfer CCD or full-frame CCD based motion picture camera that will operate within the optical constraints of existing 35 mm motion picture lenses (the focal flange distance restricts the options for placement of the components).
Advantages of this approach include that the camera does not require an ILT sensor architecture, has higher fill factor, simpler clocking, large die size achieved through stitching not currently believed to be available to ILT designs, and does not require micro-lenses for recovery of fill factor and hence improved MTF (modulation transfer function).